The invention relates to a crane having a laterally projecting crane jib on which a hoisting device is disposed and which is connected to at least one support body which, together with the crane jib, can travel along an upper running rail and a lower running rail via travelling mechanisms, wherein in each case the upper and the lower running rails and accordingly the travelling mechanisms are disposed so as to be vertically spaced apart from each other.
European patent document EP 0 544 139 B1 discloses a bracket crane for moving loads by means of at least one crane jib. A hoisting device is accommodated on the crane jib so as to be able to travel by means of a trolley and is used to raise and lower the load. The crane jib is guided on, and can travel along, an upper and lower running rail in a freely laterally projecting manner on one end via an upper and a lower travelling mechanism. The travelling mechanisms each comprise two running wheels and are attached to the crane jib so as to be offset with respect to each other horizontally and vertically in relation to the longitudinal direction of the crane jib. The running rails extend in parallel with each other horizontally and transversely with respect to the crane jib and are attached to a wall or an elevated support structure. The lower travelling mechanism is attached by means of a downwardly directed vertical holder to an end of the crane jib remote from the free end of the crane jib. The running wheels of the lower travelling mechanism run on a lower side of the lower running rail. The running wheels of the upper travelling mechanism run on the upper running rail. The upper travelling mechanism is attached directly to the crane jib. In this manner, the forces or moments resulting from the acceleration or own weight of the crane elements and any load are fed into the running rails or supports via the running wheels of the travelling mechanisms. The crane jib may also be pivotable in a horizontal plane.
German patent document DE 1 135 640 B discloses a comparable bracket crane having a crane jib which is fixedly connected to a bracket acting as a travelling mechanism girder. The bracket crane consists substantially of two parts which are fixedly connected together at the destination of the bracket crane. The frame-shaped bracket is composed of a T-shaped girder and a U-shaped girder for this purpose. The crane jib is fixedly connected to a horizontal region of the T-shaped girder. The T-shaped girder is also fixedly connected at its two ends, in each case via a flange, to each vertical limb of the U-shaped girder. Disposed on the base of the T-shaped girder and, in a vertically offset manner, on the limbs of the U-shaped girder of the assembled bracket are pairs of travelling mechanisms or running wheels for feeding forces or moments into an upper and a lower longitudinal rail and for travelling on the longitudinal rails.
German laid-open document DE 100 21 297 A1 discloses a bridge crane having a main girder which can travel transversely with respect to its longitudinal direction along two running rails extending in parallel. For this, a head girder provided with travelling mechanisms is disposed in each case on the opposite ends of the main girder and the head girders are used to support the main girder on the running rails. The head girders are releasably attached by means of screws to the main girder via in each case a connection part having angle plates. A hoisting device is also suspended on the main girder and can travel along the main girder.
Comparable bridge cranes having main girders fixedly screwed to head girders are also known from documents DE 1 229 262 A and DE 1 175 840 A, laid open for public inspection.